It has been known in the art since U.S. Pat. 3,278,263 to prepare a viscous paste for synthesis of chromium dioxide by combining chromium trioxide (CrO.sub.3), chromic oxide (Cr.sub.2 O.sub.3) and water. The Cr.sub.2 O.sub.3 component is typically obtained by the thermal decomposition of expensive ammonium dichromate. U.S. Pat. No. 4,045,544, disclosed that this viscous paste could be productively heated in an annular can under pressure to produce ferromagnetic chromium dioxide. Yet, despite continued efforts to reduce manufacturing costs, ferromagnetic chromium dioxide remains more expensive to produce than iron oxide-based products.